import type { languages } from 'monaco-editor';

// Build regex patterns for each keyword category.
// Longer patterns must come first so alternation prefers them.
const pipelinePattern = 'json|logfmt|regexp|pattern|unpack|line_format|label_format|drop|keep|unwrap|decolorize';
const rangeFuncPattern =
  'rate_counter|count_over_time|bytes_rate|bytes_over_time|' +
  'sum_over_time|avg_over_time|max_over_time|min_over_time|' +
  'first_over_time|last_over_time|stdvar_over_time|stddev_over_time|' +
  'quantile_over_time|absent_over_time|rate';
const aggrPattern = 'sort_desc|approx_topk|stddev|stdvar|bottomk|topk|sum|avg|min|max|count|sort';
const otherPattern = 'group_left|group_right|without|ignoring|offset|bool|vector|by|and|or|on';

export function buildMonarchLanguage(): languages.IMonarchLanguage {
  return {
    defaultToken: '',
    tokenPostfix: '.loki',

    brackets: [
      { open: '{', close: '}', token: 'delimiter.curly' },
      { open: '[', close: ']', token: 'delimiter.square' },
      { open: '(', close: ')', token: 'delimiter.parenthesis' },
    ],

    tokenizer: {
      root: [
        // Whitespace
        [/[ \t\r\n]+/, 'white'],

        // Comments: #
        [/#.*$/, 'comment'],

        // Strings
        [/"/, { token: 'string.quote', next: '@string_double' }],
        [/'/, { token: 'string.quote', next: '@string_single' }],
        [/`/, { token: 'string.quote', next: '@string_backtick' }],

        // Duration
        [/\d+(?:\.\d+)?(?:ns|us|µs|ms|s|m|h)\b/, 'type.duration'],

        // Bytes
        [/\d+(?:\.\d+)?(?:B|kB|MB|GB|TB|KB|KiB|MiB|GiB|TiB)\b/, 'type.bytes'],

        // Numbers
        [/\d+\.\d+/, 'number.float'],
        [/\d+/, 'number'],

        // Operators (order matters: longer patterns first)
        [/!=/, 'operator'],
        [/!~/, 'operator'],
        [/=~/, 'operator'],
        [/>=/, 'operator'],
        [/<=/, 'operator'],
        [/==/, 'operator'],
        [/[=<>]/, 'operator'],

        // Pipe operators
        [/\|~/, 'operator.pipe'],
        [/\|=/, 'operator.pipe'],
        [/\|/, 'operator.pipe'],

        // Brackets and punctuation
        [/\{/, 'delimiter.curly'],
        [/\}/, 'delimiter.curly'],
        [/\[/, 'delimiter.square'],
        [/\]/, 'delimiter.square'],
        [/\(/, 'delimiter.parenthesis'],
        [/\)/, 'delimiter.parenthesis'],
        [/,/, 'delimiter.comma'],

        // Keywords (must come before generic identifier)
        [new RegExp('\\b(?:' + pipelinePattern + ')\\b'), 'keyword.pipeline'],
        [new RegExp('\\b(?:' + rangeFuncPattern + ')\\b'), 'keyword.function'],
        [new RegExp('\\b(?:' + aggrPattern + ')\\b'), 'keyword.aggregation'],
        [new RegExp('\\b(?:' + otherPattern + ')\\b'), 'keyword'],

        // Generic identifier
        [/[a-zA-Z_][\w]*/, 'identifier'],

        // Catch-all
        [/[;:]/, 'delimiter'],
      ],

      string_double: [
        [/[^\\"]+/, 'string'],
        [/\\./, 'string.escape'],
        [/"/, { token: 'string.quote', next: '@pop' }],
      ],

      string_single: [
        [/[^\\']+/, 'string'],
        [/\\./, 'string.escape'],
        [/'/, { token: 'string.quote', next: '@pop' }],
      ],

      string_backtick: [
        [/[^`]+/, 'string'],
        [/`/, { token: 'string.quote', next: '@pop' }],
      ],
    },
  } as languages.IMonarchLanguage;
}